Glass sheets have been used in the manufacture of display devices such as LCD TVs, computer monitors and handheld devices. For example, in a modern LCD TV set, a piece of thin glass sheet with pristine surface quality is used as a substrate for TFT and other electronic devices, and another piece is used as a substrate for the color filter. Recently, thin glass sheets started to find use as cover sheets for the screens of handheld devices and TV sets as well.
The thin glass sheets are typically made by using a fusion down-draw process, which is pioneered by Corning Incorporated, Corning, N.Y., U.S.A. (hereinafter “Corning Incorporated”), a float forming process, or other forming methods, from glass melt. Because these forming processes are typically continuous on an industrial scale, as-formed glass ribbons immediately exiting the forming facility normally need to be cut into multiple, discreet glass sheets before being shipped to device manufacturers. Furthermore, the as-cut glass sheets produced at the glass forming production lines normally have sizes that can accommodate the manufacture of multiple devices on the same surface simultaneously. At a certain point of time, such large glass sheets need to be cut into smaller size of the final devices.
One traditional approach for cutting continuous glass ribbons and large glass sheets comprises a first step of forming a scribe-line on a surface by using a mechanical scoring wheel, followed by bending the glass ribbon or sheet along the score-line so that smaller, discreet glass sheets are separated from the mother ribbon or sheet. This method has been used for making glass sheets having a relatively large thickness, such as 1.0 mm, 700 μm and 600 μm, successfully. Another approach demonstrated to be effective uses a laser beam for forming the score-line in the first step, followed by bending and separation. Usually, during the first laser scoring step, a laser beam is projected to the glass sheet surface, which is absorbed by the glass sheet, thereby heating the glass sheet to an elevated temperature. Normally, a cooling fluid jet, such as water jet or air jet, is then applied to the heated surface, causing a tensile stress, which, if significant enough, can cause a pre-formed initiation defect on the glass to propagate into a score-line with a given depth.
Currently, the demand of ever lighter display devices have pushed the glass substrates for display devices toward ever lower thicknesses, such as 400 μm, 300 μm, 200 μm, 100 μm and even lower. It has been found that, for glass sheets with such thin thicknesses, the score-and-break process, whether involving a laser scoring or mechanical scoring step, cannot be utilized to consistently and reliably produce glass sheets with high-quality edges.
Laser full-body cutting processes were proposed previously for cutting thin glass sheets. However, reliability and edge quality of those processes need further improvement. In addition, those processes can be very complex.
Hence, there is a need of a reliable thin glass sheet cutting method. The present invention meets this and other needs.